1. Field of the Invention
The present invention is generally in the field of electrical circuits. More particularly, the invention is in the field of line drivers for transmission lines.
2. Background Art
Line drivers, such as current mode line drivers in transmitter modules, can be utilized in set-top boxes, cable modems, routers, computer interfaces, and other electronic devices to drive transmission lines, such as Ethernet transmission lines. A line driver, such as a current mode line driver, can include a current digital-to-analog converter (IDAC) for receiving a digital input waveform. The line driver can be configured to provide an analog output waveform corresponding to the digital input waveform. However, the analog output waveform can be required to meet stringent rise and fall time specifications, such as the rise and fall time specifications required by, for example, a 100TX Ethernet data transmission standard.
A conventional approach can include providing analog RC filtering in the line driver to achieve an analog output waveform having rise and fall times that meet required specifications. However, process, voltage, and temperature variations in R (resistance) and C (capacitance) values can cause the rise and fall times of the analog output waveform to fail to meet the required specifications. As a result, the conventional approach can require a calibration circuit to provide RC time constant calibration so as to cause the analog output waveform to meet the required rise and fall time specifications. However, the calibration circuit can undesirably increase line driver design complexity and layout area.